calling a subroutine from a dll

[immoral]

Dear All,

Hope you have a good time. I work on a VB .net plug in . When I call two subroutines from another class as below: I see the first msgbox result but after I click ok on the first msgbox, both, my plug in and main programme will be closed.

Call cls1DEngine.set_openmi_ief(m_1DProjectFilename,  m_1DProjectFilename.Length)
          MsgBox("set_openmi passed")
          Call cls1DEngine.initialise()
           MsgBox("set_openmi passed")

these subroutines call two subroutine from ILM_omi.dll and they appear in Cls1DEngine as below:

<DllImport("C:\bin\ILM_omi.dll")> _
    Shared Sub set_openmi_ief(ByVal FileName As String, ByVal Length As Integer)
     ' No code here
    End Sub
 
    <DllImport("C:\bin\ILM_omi.dll")> _
   Shared Sub initialise()
        ' No code here
    End Sub

Does any body know what the problem is? And also why all related windows closing down when initialise sub is called.

Many Thanks,
Reza